#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<assert.h>
#include<sys/types.h>
#include<sys/wait.h>
#include<unistd.h>

#define LEFT "["
#define RIGHT "]"
#define LABLE "#"
#define LINE_SIZE 1024
#define DELIM " \t"
#define ARGC_SIZE 32
#define EXIT_CODE 44



int lastcode=0;
int quit=0;
extern char **environ;
char commandline[LINE_SIZE];
char *argv[ARGC_SIZE];
char pwd[LINE_SIZE];

char myenv[LINE_SIZE];

const char *getusername()
{
  return getenv("USER");
}

const char *_gethostname(){
  return getenv("HOSTNAME");
}

void getpwd(){
  getcwd(pwd,sizeof(pwd));
}

void Interact(char *cline,int size){
  getpwd();
  printf(LEFT"%s@%s %s"RIGHT""LABLE" ",getusername(),_gethostname(),pwd);
  char *s=fgets(cline,size,stdin);
  assert(s);
  (void)s;
  cline[strlen(cline)-1]='\0';
}

int splitstring(char cline[], char *_argv[]){
  int i=0;
  argv[i++]=strtok(cline,DELIM);
  while(_argv[i++]=strtok(NULL,DELIM));
  return i-1;
}

void NormalExcute(char* _argv[]){ 
  pid_t id=fork();
  if(id<0){
    perror("fork");
    return ;
  }else if(id==0){
    execvp(_argv[0],_argv);
    exit(EXIT_CODE);
  }else{
    int status =0;
    pid_t rid=waitpid(id,&status,0);
    if(rid==id){
      lastcode=WEXITSTATUS(status);
    }
  }
}


int buildCommand(char *_argv[], int _argc){
  if(_argc==2 && strcmp(_argv[0],"cd")==0){
    chdir(argv[1]);
    getpwd();
    sprintf(getenv("PWD"),"%s",pwd);
    return 1;
  }else if(_argc==2&&strcmp(_argv[0],"export")==0){
    strcpy(myenv,_argv[1]);
    putenv(myenv);
    return 1;
  }else if(_argc==2&&strcmp(_argv[0],"echo")==0){
    if(strcmp(_argv[1],"$?")==0){
      printf("%d\n",lastcode);
      lastcode=0;
    }
    else if(*_argv[1]=='$'){
      char *val=getenv(_argv[1]+1);
      if(val) printf("%s\n",val);
    }else{
      printf("%s\n",_argv[1]);
    }
    return 1;
  } 
  if(strcmp(_argv[0],"ls")==0){
    _argv[_argc++]="--color";
    _argv[_argc]=NULL;
  }
  return 0;
}



int main(){
  char commandline[LINE_SIZE];
  int  quit=0;
  while(!quit){
    Interact(commandline,sizeof(commandline));
    int argc=splitstring(commandline,argv);
    if(argc==0) continue;
    //printf("echo: %s\n",commandline);
    int n=buildCommand(argv,argc);
    if(!n) NormalExcute(argv);
  }
  return 0;
}
